Tone color forming circuit in electronic musical instrument

ABSTRACT

A tone-color forming circuit in an electronic musical instrument comprises fundamental tone and second harmonic tone producing circuits operable in mutual in-phase relationship, a first switching circuit of a longer decaying time connected with the outputs of the fundamental and second harmonic producing circuits, a second switching circuit of a shorter decaying time connected with the output of the fundamental tone producing circuit and with the phase-reversed output of the second harmonic producing circuit, a first filter and a second filter of different characteristics coupled respectively with the outputs of the first and second switching circuits, and a mixing circuit, whereby a musical tone signal of double-fold decay can be obtained from the mixing circuit.

O United States Patent 1191 1111 3,789,071

Niinomi June 12 1973 TONE-COLOR FORMING CIRCUIT IN 3,176,060 3/1965 Bissonette et al 84/1.01 ELECTRONIC MUSICAL INSTRUMENT 3,429,976 2/l969 Tomclk 84/l.l2 3,535,969 10 1970 Bunger 84/1.ll [75] In en Naoyukl Nlmoml, Hamamatsu, 3,558,792 1/1971 Kniepkamp.... 84/l.01 Japan 3,591,699 7/1971 Cutler 84/l.ll

73 Ass nee: Ni on Gakki Seizo Kabushiki 1 lg Hamamatswshi Primary Examiner-Richard B. Wilkinson shizuollaken Japan Assistant ExaminerStanley J. Witkowski Attorney-Holman & Stern [22] Filed: Dec. 29, 1971 [21] Appl. No.: 213,458 [57] ABSTRACT A tone-color forming circuit in an electronic musical [30] Foreign Application p Data instrument comprises fundamental tone and second Dec 29 1970 la an 45/121658 harmonic tone producing circuits operable in mutual p in-phase relationship, a first switching circuit of a 52 us or. 84/1.19, 84/122, 84/126, decaying time mmected the W? t 84/1 23 fundamental and second harmonic producing c1rcu1ts, [51] Int Cl Gloh H a second switching circuit of a shorter decaying time [58] Field 114 13 connected with the output of the fundamental tone 6 l producing circuit and with the phase-reversed output of the second harmonic producing circuit, a first filter d a second filter of different characteristics coupled [56] References Cited an respectively with the outputs of the first and second UNITED STATES PATENTS switching circuits, and a mixing circuit, whereby a muggfil y ct sical tone signal of double-fold decay can be obtained 1 1ams f th 2,879,387 3/1959 Kahn 84/122 X mm 6 mlxmg clrcul 3,006,228 10/1961 White 84/101 4 Claims, 7 Drawing Figures SWITCHING CIRCUlT 3 5 LOW PASS FILTER T2 T4 7 FLIFLFLOP \MlXlNG CIRCUlT T5 7 (4) (8) 4 SWITCHING 6 RESONANCE l CIRCUIT Q'YPE FILTER 2 FLIP-FLOP Ts/l TONE-COLOR FORMING CIRCUIT IN ELECTRONIC MUSICAL INSTRUMENT BACKGROUND OF THE INVENTION This invention relates to tone-color forming circuits in electronic musical instruments, and more particularly to a new and advanced circuit capable of producing instrument signals simulating the sound of a bass guitar or the like having a double-fold attenuation characteristic accompanied by variation in tone-color.

As is well known, a musical instrument such as a bass guitar produces a musical tone characterized by double-fold decay accompanied by varying tone-color. Heretofore, when attempts were made to simulate the bass guitar or the like in an electronic musical instrument, difficulties have been encountered in the creation of the double-fold decaying features, and as far as I am aware, none of such attempts have yet succeeded in creating a music tone compatible with that of the bass guitar or the like.

SUMMARY OF THE INVENTION Therefore, a primary object of the present invention is to provide tone-color forming circuit in an electronic musical instrument which can simulate the sound of a bass guitar or the like.

Another object of the invention is to provide a tonecolor forming circuit in an electronic musical instrument which can create a tone-color simulating the bass guitar or the like, wherein is included a second harmonic component in addition to the fundamental tone, and the second harmonic component reappears after it has once disappeared during the attenuation of the resultant music tone.

These and other objects of the present invention can be achieved by a tone-color forming circuit in an electronic musical instrument, which circuit comprises a fundamental tone producing circuit, a second harmonic producing circuit producing two signals of the same frequency but of a reversed phase relation, a first switching circuit of a longer decaying time characteristic coupled with the outputs of these fundamental and second harmonic producing circuits, a second switching circuit of a shorter decaying time characteristic coupled with the outputs of these two circuits but in the reversed phase (polarity) for the output of the-second harmonic producing circuit, first and second filters of different tone-color characteristics coupled respectively to the outputs of said first and second switching circuits, and a mixing circuit for mixing the outputs of these filters, whereby a music tone signal of a doublefold decaying envelope can be obtained from the mixing circuit.

The nature, principle, and the utility of the present invention will be more clearly understood from the hereinafter described detailed description of the invention with respect to a preferred embodiment thereof when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a block diagram of a tone-color forming cir- FIGS. 3(a) and 3(b) are characteristic curves representing the characteristics of filters included in the circuit shown in FIG. 1; and

FIGS. 4(a) and 4(b) are diagrams showing the envelope curves of 8 and 4 tone signals included in the output musical tone signal of this circuit.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1 showing a tone-color forming circuit constituting an embodiment of the present invention, a tone signal is applied to an input terminal T, of the tone-color forming circuit and hence to a flip-flop l of 4-foot register tone. The output of the 4-foot register flip-flop 1 is then applied to an 8-foot register flipflop 2 to be frequency-divided therein into one-half. The 8-foot register tone corresponds to a fundamental tone for the tone-color forming circuit, and the 4-foot register tone corresponds to a second harmonic tone for the same circuit.

A signal applied to an input terminal T, does not include only one special frequency. The frequencies so applied are decided by what particular note switching circuits share in. Assuming for instance that the switching circuits share in C -note (fundamental frequency 261.6 Hz), an output frequency from the flip-flop 2 is 261.6 Hz and an output frequency from the flip-flop 1 is 523.3 Hz. Accordingly, an input frequency to the flip-flop 1 becomes 1046.5 H2. In general, four-foot register means a resistor wherein the produced tones have frequencies which are respectively one octave higher than nominal frequencies. Since the flip-flop operates to divide an input frequency by one-half, it is necessary to previously apply to the input terminal a tone signal having a frequency one octave higher than that of 4-foot register tone in order to obtain the 4-foot register tone from the flip-flop 1.

From terminals T and T of the 4-foot register flipflop 1, two 4-foot register tone signals of mutually opposite phase relationship are produced and are supplied to switching circuits 3 and 4, respectively. The output signal from the flip-flop 2 for 8-foot register tone is delivered from a terminal T thereof supplied to both of the switching circuits 3 and 4.

The decaying characteristic of the switching circuit 3 is selected to be one which gradually decays within about 1,000 milliseconds as shown in FIG. 2(a). The output signal from the switching circuit 3 is passed through a low-pass filter 5 of a characteristic such that a frequency component lower than about 130 Hz is emphasized as indicated in FIG. 3(a). The output signal from the filter 5 is thereafter supplied to a mixing circuit 7.

On the other hand, the decaying characteristic of the switching circuit 4 is of a kind which sharply decays within milliseconds as shown in FIG. 2(b). The output signal from the switching circuit 4 is thereafter passed through a resonance type filter 6 of a characteristic as shown in FIG. 3(b) such that a frequency portion near about 500 Hz is emphasized. The output from the filter 6 is also supplied to the mixing circuit 7. Within the mixing circuit 7, the output signals from the filters 5 and 6 are mixed, and the output signal of this tone-color forming circuit is obtained from an output terminal T of the mixing circuit 7.

It is to be noted that the signal level of the output of the switching circuit 4 is selected to be higher than that of the output of the switching circuit 3. In the tonecolor forming circuit thus organized and set, when the 8-foot tone signal only is taken into consideration, the two output signals of the same flip-flop 2 for 8-foot register tone, which are of the same phase, areswitched respectively in the switching circuits 3 and 4, which have predetermined decaying characteristics as described above, and are then passed through the lowpass filter 5 and the resonance type filter 6 to the mixing circuit 7.

As to the switching circuits 3 and 4, it will be apparent to those skilled in the art that suitable structure may be chosen therefor in a manner that the signal level of the output of switching circuit 4 is higher than the signal level of the switching circuit 3. An example of suitable structure for the switching circuits may be derived from the illustration in U. S. Pat. No. 3,170,020.

Accordingly, the envelope of the resultant 8-foot tone signal obtained from the mixing circuit 7 has an envelope curve as shown in FIG. 4(a) rapidly decaying during the initial 100 milliseconds and slowly decaying during the remaining 900 milliseconds.

When the 4-foot tone signal is now taken into consideration, two output signals of 4-foot tone, in an opposite phase relationship to each other, are respectively passed through the switching circuits 3 and 4 and the low-pass filter 5 and the resonance type filter 6, respectively, to the mixing circuit 7.

Since the signal level of the output of the switching circuit 4 is selected to be higher than that of the output of the switching circuit 3, the output signal from the mixing circuit 7 initially contains the 4-foot tone signal obtained from the terminal T (of the opposite phase), whereby the 4-foot tone signal obtained from the terminal T (of the primary phase) is cancelled. However, in the meantime, the 4-foot tone signal obtained from the terminal T decays more quickly than that obtained from the terminal T depending on the characteristics of the switching circuits 3 and 4, and when the magnitudes of the 4-foot tone signals obtained from the terminals T and T become equal, the 4-foot tone signal component contained in the output of the mixing circuit 7 is nullified.

After this instant, because of the quick attenuation characteristic of the switching circuit 4, the 4-foot tone signal of the reversed phase obtained from the terminal T fades, and the 4-foot tone signal in phase with the 8-foot tone signal obtained from the terminal T is predominant in the output of the mixing circuit 7. After 100 milliseconds, no 4-foot tone signal exists in the output of the switching circuit 4. Thus, in the output of the mixing circuit 7, the initially appearing 4-foot tone signal disappears in the course of the decaying and then reappears as shown in FIG. 4(b).

Although in the above description, the 4-foot and 8- foot tone signal have been described separately, the actual output tone signal obtained from the mixing circuit 7 contains both of these component signals, whereby a variation effect in the tone color wherein the second harmonic component disappears once in the course of the decaying and reappears thereafter can be obtained in the output tone signal delivered from the mixing circuit 7. Such an effect of variation in the tone-color is further accentuated by the disposition of filters of low pass and resonance characteristics at the subsequent stages of the switching circuits 3 and 4, respectively.

By the above described organization of the tonecolor forming circuit according to the present invention, a musical tone signal having double-fold attenuation characteristics accompanied by a tone-color variation during the attenuation can be obtained, and a musical instrument simulating the guitar and the like with naturalness of auditory sensation can be produced by employing the tone-color forming circuit according to the present invention.

I claim:

I. A tone-color forming circuit in an electronic musical instrument, comprising: a fundamental tone producing circuit; a second harmonic producing circuit producing two signals of the same frequency but of a reversed phase relationship; a first switching circuit having a predetermined decaying time connected with the output of said fundamental tone producing and the output of the second harmonic producing circuit without phase reversal, a second switching circuit having a decaying time shorter than said predetermined time and coupled with the output of said fundamental tone producing circuit and with the output in the reversed phase of the second harmonic producing circuit; a first filter and a second filter having outputs and being of different tone-color characteristics and coupled respectively with the outputs of the first and second switching circuits; and a mixing circuit for mixing the outputs of said filters, whereby a musical tone signal of an envelope having a double-fold decaying characteristic can be obtained from the mixing circuit.

2. A tone forming circuit as set forth in claim 1 wherein said first switching circuit of said predetermined decaying time has a decaying period of the order of 1,000 milliseconds, and said second switching circuit having a shorter decaying time has a decaying period of the order of milliseconds.

3. A tone-color forming circuit as set forth in claim 1 wherein said first filter is made in the form of a lowpass filter, and said second filter is made in the form a resonance type filter.

4. A tone-color forming circuit as set forth in claim 1 wherein an output level of said second switching circuit is selected to be higher than an output level of said first switching circuit.

* I I k of I 

1. A tone-color forming circuit in an electronic musical instrument, comprising: a fundamental tone producing circuit; a second harmonic producing circuit producing two signals of the same frequency but of a reversed phase relationship; a first switching circuit having a predetermined decaying time connected with the output of said fundamental tone producing and the output of the second harmonic producing circuit without phase reversal, a second switching circuit having a decaying time shorter than said predetermined time and coupled with the output of said fundamental tone producing circuit and with the output in the reversed phase of the second harmonic producing circuit; a first filter and a second filter having outputs and being of different tone-color characteristics and coupled respectively with the outputs of the first and second switching circuits; and a mixing circuit for mixing the outputs of said filters, whereby a musical tone signal of an envelope having a double-fold decaying characteristic can be obtained from the mixing circuit.
 2. A tone forming circuit as set forth in claim 1 wherein said first switching circuit of said predetermined decaying time has a decaying period of the order of 1,000 milliseconds, and said second switching circuit having a shorter decaying time has a decaying period of the order of 100 milliseconds.
 3. A tone-color forming circuit as set forth in claim 1 wherein said first filter is made in the form of a low-pass filter, and said second filter is made in the form of a resonance type filter.
 4. A tone-color forming circuit as set forth in claim 1 wherein an output level of said second switching circuit is selected to be higher than an output level of said first switching circuit. 